1. Field
Example embodiments relate to methods of fabricating a ZnO thin film structure and a ZnO thin film transistor (TFT), and a ZnO thin film structure and a ZnO TFT.
2. Description of the Related Art
Zinc oxide (ZnO) as a metal oxide semiconductor may be applied to TFTs, sensors, optical wave guides and/or piezoelectric elements. In general, a ZnO thin film grown at a higher temperature of about 400° C. or more may have higher quality. However, such higher temperature growth limits the materials that may be used to form a substrate and thus may not be applied to a plastic substrate which may be susceptible to heat damage.
In the related art, a substrate may be heated at a temperature between about 350° C. and about 450° C. during growth of ZnO, and a ZnO crystal may be grown at a temperature between about 600° C. and about 900° C. In a general ZnO TFT, a channel may be formed of ZnO; a source, a drain, and a gate may be formed of metals (e.g., Mo); and a gate insulator may be formed of SiNx and/or SiO2. The ZnO TFT may be covered with a protection layer and/or a passivation layer formed of SiO2 and/or SiNx so as to be insulated and protected from other elements formed on the ZnO TFT.
A ZnO thin film may be formed in an oxygen atmosphere by metal organic chemical vapor deposition (MOCVD) and/or sputtering. Semiconductor characteristics of a ZnO thin film may be sensitive to the amount of oxygen content, and thus the content of oxygen may be adjusted. In general, an oxygen partial pressure may be appropriately adjusted with respect to an atmosphere gas to adjust the content of oxygen during depositing of ZnO. However, this method may be relatively difficult and thus may not be successful. It may be difficult to more easily obtain desired semiconductor characteristics of ZnO through the adjustment of the oxygen partial pressure. As a result, dopants must be added to ZnO to obtain desired semiconductor characteristics.